Kobo Clara HD - SD card Upgrade

[learningtech]

I'm new to all this and my Kobo Clara got stuck looping.

I read the SD card upgrade method and did that successfully, but in the process I damaged the screen putting it back together. It's stuck on Danish language and the settings option isn't working working when I try to click it. It's that corner where the screen has a line across it. It doesn't have a physical crack in the screen, but the right hand corner has a diagonal line across it (still shows the screen options here) and the top right corner has a grey patch which is not showing the screen image.

I imagine I have ruined it forever, have I? Is there anything I can do? Could it be the SD image was corrupted?

Any advice would be greatly appreciated, its the first time I've attempted to repair a gadget.